1. Field of the Invention
The present invention relates to analog amplifier circuits with variable signal gain, and in particular, to analog amplifier circuits having variable signal gain according to a monotonic transfer function.
2. Description of the Related Art
Analog amplifier circuits with variable signal gains are used in many applications. One of many examples would be the numerous analog amplifier circuits needed in a video system for processing, conditioning and displaying the video image signals. Indeed, video circuits in particular require such amplifier circuits to have truly monotonic transfer functions with respect to the signal gains. Any nonlinearities or discontinuities in the transfer function can introduce significant signal errors, particularly in high resolution color image displays.
Accordingly, it would be desirable to have an analog amplifier circuit with a variable gain according to a monotonic transfer function and a simple and reliable circuit structure.